The class featured 12 riders representing the county with Northallerton Olympian Nicola Wilson finishing fourth on JL Dublin.
Victory went to Gemma Tattersall on Quicklook V, who edged out Laura Collett on Dacapo with Emily King third on Brookleigh as GB riders filled the first eight places.
Yorkshire’s riders also excelled with 25-year-old Richardson next best behind Wilson in 22nd on Caraghs Buffet after a clear round inside the time over cross country.
“It was an incredible experience and I felt extremely lucky to be there competing there against all the top riders,” said Richardson. “I am absolutely over the moon with my little horse.”
Richardson finished two places above another Bramham debutante in Wetherby’s Morgan Kent, who is thriving as an eventer.
Kent is better known as a showjumper and went double clear on Felda inside the time to finish 24th. Richmond’s Katie Magee finished 30th on Enceladus, followed by Womersley’s Sophie Platt on Be Be III in 35th.
Both riders were clear over cross country with Platt also inside the time and also competing on Caesar II, who was retired over cross country.
In 42nd, Bingley’s Charlotte Brear emotionally completed her fourth Bramham on board Manor Missile who has recovered from laminitis. Both Brear and Scarborough’s Phil Brown, who finished 46th on Harry Robinson, were clear over cross country.
Harrogate’s Hazel Towers finished 50th on Simply Clover, while Weeton’s James Rushbrooke completed his first Bramham, finishing 52nd on Zelandnew BK.
York’s Christopher Whittle was another Bramham debutante and he went clear over cross country to finish 54th on Skip Mill.
Thirty four years after her mum Helen won the Under-25 class, Breckenbrough’s Chloe Bell also completed her first Bramham, finishing 56th on Javas Spice. Bedale’s Sara Bowe eventually retired Kilcoltrim Mermist over cross country.